An impeller used for a vehicular air conditioner or the like generally has a substantially truncated cone-shaped hub which expands in diameter toward one side in the axial direction, and a plurality of vanes provided on the outer circumferential surface of the hub at a predetermined interval in the circumferential direction and inclined in one direction. A manufacturing method of such an impeller having a hub with a plurality of vanes is known (for example, Patent Document 1).
In Patent Document 1, as shown in FIG. 11, an impeller 100 has a substantially truncated cone-shaped hub 101 which expands in diameter toward one side in the axial direction and six vanes 103 provided in on an outer circumferential surface 102 of the hub 101 at a predetermined interval in a circumferential direction and inclined in one direction.
The impeller 100 is made of an aluminum alloy and is manufactured by a die-casting method. The hub 101 and the vanes 103 are formed integrally with each other within a possible shape range by the die-casting method, and then vane positions are corrected by lifting the vanes 103 in a required range of the vanes 103.
Each of the vanes 103 has a shape that is inclined toward the adjacent one of the vanes 103. In order to improve the performance of the impeller 100, it is desirable to increase the number of the vanes 103 and to change the angle of the vanes 103 with respect to the outer circumferential surface 102. However, it is difficult to apply the manufacturing method of the impeller of Patent Document 1 to a resin impeller. In this regard, a manufacturing method of an impeller using a slide die is known (for example, Patent Document 2).
In Patent Document 2, as shown in FIG. 12, the mold includes a movable die and a fixed die 111 capable of opening/closing in the axial direction of the impeller 110, a slide support portion 112 movable in a direction perpendicular to the axial direction of the impeller 111, and a slide die 113 supported by the slide support portion 112. Grooves 114 radially formed in the fixed die 111 guides the slide support portion 112.
The slide die 113 is provided on the slide support portion 112 rotatably around a rotation axis 115 along a slide direction. Therefore, when the slide support portion 112 retracts after forming the impeller 111, the slide die 113 is rotated and demolded along the shape of the vanes 116 of the impeller 111. Compared to the technique of Patent Document 1, in the technique of Patent Document 2, the number of vanes of the impeller is increased.
However, the increase in the number of the vanes is limited in the technique of Patent Document 2, considering the space for the slide die 113. In addition, because the range in which the slide die 113 can rotate with respect to the slide support portion 112 is limited, it is not possible to change the angle of the vanes 103 with respect to the outer circumferential surface of the hub to achieve a desired shape. For these reasons, it is difficult to obtain a higher performance impeller with further increased number of vanes in a desired shape.
In addition, the slide die 113 is provided on the fixed die 111, making the mold large. Further, the slide die 113 is rotatably supported by the slide support portion 112, making the mold complicated. Therefore, there is a demand for a manufacturing method of an impeller with further increased number of vanes in a desired shape, using a mold with a small-sized and simple structure.